Undersized nails used for deck joist hangers


  #1  
Old 07-22-04, 11:56 AM
GazzBC
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Undersized nails used for deck joist hangers

Hi folks - I posted this issue under Decks etc. (see http://forum.doityourself.com/showthread.php?t=174364). I received some good advice, looking for a little more feedback in this forum.

In summary, I built a two level deck using double-shear joist hangers but did not use the appropriate joist nails (I didn't realize there was such a thing until far too late). For the flange of the hangers, I used galvanized 1 1/4" spirals that a quite a bit smaller daimeter than the joist nails. Their cross-sectional area is less than half that of the joist nails, presumably meaning they have less than half the shear strength.

The lower level deck is an easy fix according to the advice I received in the other forum (install a ledger under the hangers to provide additional support). The upper level deck, not so easy. There's no place to put supports under the joists and it's not practical to pull all of the hangers and re-nail them at this point. I'm looking for other options to give me more confidence in the safety of this deck.

My thinking is that the double shear hangers have quick-set tabs that leave a hole in the flanges that I could either sink joist nails into or a #10 screw with a washer to spread the load. It's not as good as doing it right the first time, but I'm thinking that it would have to provide some additional pull-out and shear strength. Are there any drawbacks to doing this that I'm not seeing? Any other suggestions (other than do it right next time?)
 
  #2  
Old 07-23-04, 02:05 PM
GazzBC
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Having received no feedback, I'll babble away because I like to see myself in print.

After doing some net research, I've estimated that the lateral/shear load of each hanger (based on 10d joist nails and 10d common nails for the "double shear" nails) should be 94 lbs per nail x 10 nails = 940 lbs. What I've got is 6 4d nails in the flanges of the joist hangers that I estimate at 40 lbs per nail + 4 8d nails for the double shear nails at 78 lbs per nail, meaning that my max shear load for each hanger is 552 lbs (59% of what it should be).

There is some small saving grace in that I've used 12" centres, not 16". Factor that in and it appears that the deck will carry about 75% of the load that it would if I had used the proper nails and 16" centres.

So, if I add two #10 screws per hanger (through the quick tab holes), I may gain 100-150 lbs per hanger, bringing the overall strength up to very close to what it should be (not accounting for the minor increase in dead load by going to 12" centres instead of 16").

I fully acknowledge that I have no idea of what I'm talking about, but I'm feeling a *little* better about my situation.
 
  #3  
Old 09-18-04, 11:38 PM
M
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From what I have read in the past at: www.strongtie.com/index.html

If you used this brand of connector and did not install the required size, type and number of nails http://www.strongtie.com/products/co...s.html#loadadj
you are on your own.

On another note: when did you build the deck? I assume you used Pressure treated lumber. Is it cca-c or one of the new ACQ-C (Alkaline Copper Quat Type C), ACQ-D Carbonate (Alkaline Copper Quat Type D, Carbonate formulation), CBA-A and CA-B (Copper Azole Types A and B), as well as SBX (Sodium Borate) preservatives?

If its the new type wood preservative watch those connectors closely the chemicals in the new can corrode the connectors (when moisture is introduced) to failure within months.
www.strongtie.com/ftp/bulletins/T-PTWOOD04.pdf

Unless you purchased the heavier galvanized (has a Z in the part number) or SS.

I am not trying to scare you I just wanted you to know the facts.

If it where my deck I would replace the nails with the correct ones and verify that I used the
www.strongtie.com/products/categories/zmax.html

correct hanger if the lumber has the new style PT. No matter how "MUCH TROUBLE IT WAS" If the deck was to collapse and someone was hurt I am afraid that you would be liable.

I apoligize if I seem heavy handed but, I am only trying to help.

mechrus
 
 

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